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      <title>OA办公系统 - 交互式测验</title>
      <style>
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        .quiz-header {
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        .quiz-header h1 {
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        .quiz-header p {
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            font-size: 14px;
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        .quiz-body {
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          margin-bottom: 12px;
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          transition: background-color 0.2s ease, border-color 0.2s ease;
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        .option-item:hover {
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        .option-item.selected {
            background-color: #d1e7fd;
            border-color: #4a90e2;
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        .quiz-footer {
          padding: 20px 30px;
          display: flex;
          justify-content: space-between; /* 将按钮分布在两侧 */
          align-items: center;
          min-height: 65px; /* Reserve space */
        }

        .nav-btn {
          background-color: #4a90e2;
          color: white;
          border: none;
          border-radius: 8px;
          padding: 10px 20px;
          font-size: 16px;
          font-weight: 500;
          cursor: pointer;
          transition: background-color 0.2s ease, transform 0.2s ease;
          box-shadow: 0 4px 12px rgba(0,0,0,0.15);
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        #next-btn {
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        .nav-btn:hover {
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        .nav-btn:disabled {
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        .result-box {
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        .final-score-container h2 {
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            border-radius: 12px;
            padding: 20px;
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        .score-details td {
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        .score-details td:last-child {
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            font-weight: 700;
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        .report-actions button {
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        .hint-container {
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            border-radius: 8px;
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            font-size: 15px;
            line-height: 1.6;
            display: none; /* 默认隐藏 */
        }
      </style>
    </head>
    <body>
      <div class="main-wrapper">
          <div class="quiz-container">
            <div class="quiz-header">
              <h1>OA办公系统 - 交互式测验</h1>
              <p>检验你对文档内容的理解程度</p>
            </div>
            <div id="quiz-content">
                <div class="quiz-body">
                    <div class="progress-bar">
                        <div id="progress-indicator"></div>
                    </div>
                    <div id="question-container">
                      <p id="question-text"></p>
                      <ul class="options-list" id="options-list"></ul>
                    </div>
                    <div id="result-container"></div>
                    <div id="hint-container" class="hint-container"></div>
                </div>
                <div class="quiz-footer" id="quiz-footer">
                  <button id="prev-btn" class="nav-btn">上一题</button>
                  <button id="hint-btn" class="nav-btn" style="background-color: #ffc107; color: #333; box-shadow: 0 4px 12px rgba(255,193,7,0.3);">提示</button>
                  <button id="next-btn" class="nav-btn">下一题</button>
                </div>
            </div>
          </div>
      </div>

      <script>
        const quizData = [
  {
    "question": "根据CAP理论，当一个分布式系统发生网络分区（Partition）时，系统设计者必须在哪两个特性之间做出权衡？",
    "options": [
      "一致性（Consistency）和持久性（Durability）",
      "原子性（Atomicity）和可用性（Availability）",
      "一致性（Consistency）和可用性（Availability）",
      "可用性（Availability）和隔离性（Isolation）"
    ],
    "correctAnswerIndex": 2,
    "explanation": "CAP理论的核心思想是，一个分布式系统最多只能同时满足一致性（C）、可用性（A）和分区容错性（P）中的两项。由于网络分区在分布式系统中是无法避免的，因此P是必须保证的。这就意味着，当分区发生时，系统必须在保证数据强一致性（所有节点数据同步，可能导致部分节点暂时不可用）和保证高可用性（所有节点都能响应，但可能返回旧数据）之间做出选择。",
    "source": "通用分布式事务核心知识 - CAP理论",
    "hint": "CAP理论指出，在分布式计算中，三个保证中你最多只能同时拥有两个。"
  },
  {
    "question": "两阶段提交协议（2PC）最主要的缺点是什么，它可能导致什么问题？",
    "options": [
      "实现过于复杂，需要引入额外的消息队列。",
      "性能开销极大，因为所有操作都需要串行执行。",
      "存在同步阻塞问题，如果协调者故障，所有参与者都会锁定资源并等待。",
      "不适用于高并发场景，因为它无法处理大量的并发请求。"
    ],
    "correctAnswerIndex": 2,
    "explanation": "2PC最显著的缺点是其同步阻塞机制。在第二阶段，如果协调者（Coordinator）在发送commit或rollback指令前发生故障，所有已锁定资源的参与者（Participants）将无限期地等待协调者的指令，导致资源无法释放，整个系统处于阻塞状态，可用性大大降低。",
    "source": "通用分布式事务核心知识 - 两阶段提交 (2PC)",
    "hint": "考虑一下当事务的“指挥官”（协调者）在下达最终命令前突然失联，会发生什么情况。"
  },
  {
    "question": "与ACID模型的强一致性不同，BASE理论是为高可用性的分布式系统设计的。BASE理论中的“E”代表什么？",
    "options": [
      "执行性（Execution）",
      "效率（Efficiency）",
      "弹性（Elasticity）",
      "最终一致性（Eventually Consistent）"
    ],
    "correctAnswerIndex": 3,
    "explanation": "BASE理论是“Basically Available”（基本可用）、“Soft state”（软状态）和“Eventually Consistent”（最终一致性）的缩写。最终一致性（E）是其核心思想，它不要求系统数据在任何时刻都保持强一致，而是允许在一段时间的“不一致”后，系统中的数据最终会达到一致状态。这种模型牺牲了强一致性来换取更高的可用性。",
    "source": "通用分布式事务核心知识 - BASE理论",
    "hint": "这个概念描述了一种允许数据在短时间内不一致，但最终会同步的状态。"
  },
  {
    "question": "在TCC（Try-Confirm-Cancel）模式中，如果“Try”阶段成功，但“Confirm”阶段因为某个参与者网络超时而失败，协调者应该采取什么措施？",
    "options": [
      "忽略失败的参与者，继续对其他参与者执行Confirm操作。",
      "对所有参与者（包括已成功的和失败的）发起“Cancel”操作，回滚预留的资源。",
      "不断重试对失败的参与者执行“Confirm”操作，直到成功为止。",
      "标记事务为不确定状态，等待人工干预。"
    ],
    "correctAnswerIndex": 1,
    "explanation": "TCC模式的精髓在于其补偿机制。如果在Confirm阶段出现任何问题导致无法完成整个事务的提交，协调者必须调用所有参与者的Cancel接口。Cancel操作是一个补偿操作，它会释放或撤销在Try阶段预留的资源，从而保证整个分布式事务的原子性，达到“要么都成功，要么都回滚”的效果。",
    "source": "通用分布式事务核心知识 - TCC模式",
    "hint": "TCC模式的核心是为每个操作都提供一个反向的补偿操作，以确保事务的原子性。"
  },
  {
    "question": "Saga模式是一种常见的长事务解决方案，它通过一系列本地事务来完成。如果Saga中的某个本地事务执行失败，系统会如何保证数据一致性？",
    "options": [
      "立即中断所有后续操作，并锁定所有已修改的数据。",
      "自动重试失败的本地事务，直到它成功为止。",
      "触发一系列与失败步骤相对应的“补偿事务”，按相反顺序撤销已完成的操作。",
      "向系统管理员发送警报，由人工介入进行数据恢复。"
    ],
    "correctAnswerIndex": 2,
    "explanation": "Saga模式的核心机制是补偿。它将一个长事务分解为多个本地事务，每个本地事务都有一个对应的补偿事务。当某个本地事务失败时，Saga协调器会按相反的顺序依次调用前面已成功执行的本地事务的补偿事务，从而将系统状态回滚到事务开始前的状态，保证了最终的数据一致性。",
    "source": "通用分布式事务核心知识 - Saga模式",
    "hint": "这种模式下，没有全局的回滚，而是通过“反向操作”来撤销已经完成的步骤。"
  },
  {
    "question": "以下哪种分布式事务解决方案对业务的侵入性最强，通常要求为每个操作显式实现`Try`、`Confirm`、`Cancel`三个接口？",
    "options": [
      "两阶段提交 (2PC)",
      "Saga 模式",
      "TCC (Try-Confirm-Cancel) 模式",
      "本地消息表模式"
    ],
    "correctAnswerIndex": 2,
    "explanation": "TCC模式对业务的侵入性最强。因为它不是在资源层（如数据库）实现，而是在业务逻辑层实现。开发者需要将一个业务操作分解为Try、Confirm、Cancel三个独立的、幂等的业务逻辑，这需要对现有业务代码进行较大的改造。相比之下，2PC对业务代码基本无侵入，而Saga和本地消息表虽然也有侵入，但通常没有TCC这样结构化的强制要求。",
    "source": "通用分布式事务核心知识 - TCC模式",
    "hint": "思考哪种方案需要你在业务代码层面，为每一个动作都设计好“预备”和“取消预备”的逻辑。"
  }
];
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        let score = 0;
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          optionsListEl.innerHTML = '';
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            nextBtn.style.display = 'block';
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            html += `<div class="source-text">来源: ${questionData.source}</div>`;
            
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                // 高亮正确答案
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                    child.style.borderColor = '#c3e6cb';
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            document.getElementById('quiz-footer').style.display = 'none';

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            const totalQuestions = quizData.length;
            const answeredCount = userAnswers.filter(a => a !== null).length;
            const wrongCount = answeredCount - correctCount;
            const skippedCount = totalQuestions - answeredCount;
            const accuracy = totalQuestions > 0 ? Math.round((correctCount / totalQuestions) * 100) : 0;
            const errorRate = totalQuestions > 0 ? Math.round((wrongCount / totalQuestions) * 100) : 0;

            const finalScoreHtml =
                '<div class="final-score-container">' +
                '<h2>答题报告</h2>' +
                '<div class="score-summary">' +
                '<div class="score-card">' +
                '<h3>得分</h3>' +
                '<p>' + correctCount + ' / ' + totalQuestions + '</p>' +
                '</div>' +
                '<div class="score-card">' +
                '<h3>正确率</h3>' +
                '<p>' + accuracy + '%</p>' +
                '</div>' +
                '<div class="score-card">' +
                '<h3>错误率</h3>' +
                '<p>' + errorRate + '%</p>' +
                '</div>' +
                '<div class="score-card score-details">' +
                '<table>' +
                '<tr><td>正确</td><td>' + correctCount + '</td></tr>' +
                '<tr><td>错误</td><td>' + wrongCount + '</td></tr>' +
                '<tr><td>未答</td><td>' + skippedCount + '</td></tr>' +
                '</table>' +
                '</div>' +
                '</div>' +
                '<div class="report-actions">' +
                '<button id="review-btn">回顾测验</button>' +
                '<button class="primary" onclick="location.reload()">再试一次</button>' +
                '</div>' +
                '</div>';

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            currentQuestionIndex = 0;
            loadQuestion();
            updateNavigationButtons(); // Ensure nav buttons are correctly displayed
        }

        // Event Delegation for options
        optionsListEl.addEventListener('click', (event) => {
            if (event.target && event.target.matches('li.option-item')) {
                // Check if the question has already been answered
                if (userAnswers[currentQuestionIndex] === null) {
                    const selectedIndex = parseInt(event.target.dataset.index, 10);
                    selectOption(selectedIndex);
                }
            }
        });

        prevBtn.addEventListener('click', goToPreviousQuestion);
        nextBtn.addEventListener('click', goToNextQuestion);
        hintBtn.addEventListener('click', showHint);
        
        // 初始加载
        loadQuestion();
      </script>
    </body>
    </html>
  